Not applicable.
This invention relates to dietary supplements. More particularly, the invention relates to dietary supplements containing conjugated linoleic acid (CLA) in a formulation that protects the CLA from oxidation.
CLA is a naturally occurring group of dienoic derivatives of linoleic acid found in the fat of beef and other ruminants. CLA is reported to have effects on both tumor development and body fat in animal models. In a study designed to further characterize the metabolic effects of CLA, CLA reduced adipose depot weight by 43% to 88%. It was also found that CLA reduced body fat by several mechanisms, including reduced energy intake, increased metabolic rate, and a shift in the nocturnal fuel mix. D. B. West et al., Effects of Dietary Conjugated Linoleic Acid on Body Fat and Energy Metabolism in the Mouse, 275 Am. J. Physiol. R667-672 (1998). In another study, it was found that dietary polyunsaturated fatty acids, specifically CLA, may positively influence the prognosis of prostatic cancer patients, thus opening the possibility of new therapeutic options. A. Cesano et al., Opposite Effects of Linoleic Acid and Conjugated Linoleic Acid on Human Prostatic Cancer in SCID Mice, 18 Anticancer Res. 1429-1434 (1998). In still another study, results were obtained supporting the view that CLA mitigates the food-induced allergic reaction. M. Sugano et al., Conjugated Linoleic Acid Modulates Tissue Levels of Chemical Mediators and Immunoglobulins in Rats, 33 Lipids 521-527 (1998).
Compared to previous generations, Americans are deficient in CLA because of lower consumption of red meat and butter fat, and because changes in cattle-feeding practices have decreased CLA content in meat and milk. For optimal CLA production, cows should graze on grass instead of being artificially fattened in feed lots. The meat of grass-fed cows contains up to four times as much CLA as meat from feed-lot cows. Today""s dairy products have only about one-third the amount of CLA they had before 1960.
One big reason for rising levels of obesity in America could be CLA deficiency. As briefly reviewed above, several animal studies showed that adding CLA to the diet resulted in leaner, more muscular bodies. A pioneering Norwegian human study found that CLA-supplemented subjects lost up to 20% of their body fat in three months without changing their diet, while the control subjects on the average gained a slight amount of body fat during the same period.
CLA has also been shown to have antioxidant properties and to prevent muscle wasting (an anti-catabolic effect). CLA became popular with muscle builders because of its ability to improve the transport of glucose, fatty acids, and protein to the muscle tissue. Part of CLA""s effectiveness in preventing obesity may lie in its ability to act as a potent insulin sensitizer, thus lowering insulin resistance and, consequently, insulin levels. K. L. Houseknecht et al., Dietary Conjugated Linoleic Acid Normalizes Impaired Glucose Tolerance in the Zucker Diabetic Fatty fa/fa Rat, 244 Biochem. Biophys. Res. Commun. 678-682 (1998). Since elevated insulin is the chief pro-obesity agent, it is enormously important to keep insulin within the normal range. By activating certain enzymes and enhancing glucose transport into cells, CLA acts to lower blood sugar levels and normalize insulin levels. Thus, besides being anti-atherogenic and anti-carcinogenic, CLA is also anti-diabetogenic. That is, it helps prevent adult-onset diabetes, characterized by insulin resistance. If recent animal results are corroborated, CLA may prove to be important not only in the prevention of diabetes, but also as a new therapy for adult-onset diabetes, aimed at lowering insulin resistance.
Still further, CLA has been found to stimulate the production of lymphocytes and of interleukin-2 and to increase the levels of certain immunoglobulins while lowering the release of immunoglobulin E associated with allergies. Improved immune function resulting from CLA can also be postulated on the basis of its ability to lower the production of immunosuppressive compounds, such as leukotrienes and series II prostaglandins and to improve insulin sensitivity (elevated insulin leads to immunosuppression).
K. N. Lee et al., Conjugated Linoleic Acid and Atherosclerosis in Rabbits, 108 Atherosclerosis 19-25 (1994), and R. J. Nicolosi et al., Dietary Conjugated Linoleic Acid Reduces Plasma Lipoproteins and Early Aortic Atherosclerosis in Hypercholesterolemic Hamsters, 22 Artery 266-277 (1997), showed that CLA lowers cholesterol and triglycerides and helps to keep arteries clean. More specifically, CLA added to the diet markedly lowers total and LDL cholesterol, lowers the LDL to HDL ratio, lowers the total cholesterol to HDL ratio, and lowers serum triglyceride levels. On autopsy, the aortas of CLA-supplemented rabbits showed less atherosclerotic plaque than controls. It is not cholesterol per se, but oxidized cholesterol that is harmful to blood vessels. Thus, CLA""s antioxidant properties may play a role in its ability to help keep blood vessels clean.
The discovery that CLA possesses peroxisome proliferator-activated receptor (PPAR) alpha and gamma activating activity was a key to understanding the mechanism responsible for its apparent lipid lowering, anabolic, and antidiabetic properties in animals and humans, and established this lipid as a strong candidate for intensive development as a future non-drug antidiabetic, lipid lowering, and anabolic agent for dietary supplements, foods, and pharmaceutical use.
Unfortunately, commercially available CLA, in free fatty acid form, has until now been unsuitable for shelf-stable dietary supplements and foods due to the extreme instability of CLA free fatty acids to oxidation. A. Zhang and Z. Y. Chen, Oxidative Stability of Conjugated Linoleic Acids Relative to Other Polyunsaturated Fatty Acids, 74 J. Am. Oil Chem. Soc. 1611-1613 (1997). In fact, previous studies have shown the half-life of CLA as a free fatty acid is only 7 hours at 75xc2x0 C. or 14 days at 25xc2x0 C., which is significantly less than that of free linoleic, linolenic, and arachidonic acids, which are themselves highly unstable to oxidation. K. Eulitz et al., Oxidation of Conjugated Linoleic Acid, in 1 Advances in Conjugated Linoleic Acid Research 55-63 (M. P. Yurawecz et al., eds., AOCS Press, Champaign, Ill., 1999).
Many CLA products in the U.S. and international markets have been evaluated and shown to be rancid and inedible at or before their stated shelf-life due to the presence of decomposition products from lipid oxidation, including lipid hydroperoxides, aldehydes, ketones, carboxylic acids, and other hydrocarbons resulting from the free radical decomposition of peroxidized CLA. Since many of these products are undesirable from an organoleptic standpoint and are also toxic, it is highly desirable and commercially valuable to develop and commercialize technology capable of maintaining CLA in its natural or reduced form for extended periods of time in capsules, powders, foods, and beverages.
Peroxides are formed in the early stages of lipid oxidation from the reaction of oxygen with unsaturated fats in the presence of catalyst, usually a divalent metal ion like iron or copper. Lipid peroxides are highly unstable and reactive and decompose spontaneously or combine with other organic compounds to form new compounds that are characteristic of a particular lipid that has been subject to oxidation.
Until now, it has not been recognized that small quantities of these peroxides, including hydrogen peroxide, can have a significant adverse impact on insulin sensitivity and glucose control in susceptible individuals. Y. M. Janssen-Heininger et al., Cooperativity between Oxidants and Tumor Necrosis Factor in the Activation of Nuclear Factor (NF)-kappaB: Requirement of Ras/mitogen-activated Protein Kinases in the Activation of NF-kappaB by Oxidants, 20 Am. J. Respir. Cell. Mol. Biol. 942-952 (1999). New research evidence indicates that reactive oxidation products, including peroxides, induce oxidative stress in humans and animals and are contra-indicated when other risk factors for the development of type 2 diabetes are present. According to recent research, oxidative stress, and hydrogen peroxide in particular, can play a role in accelerating the development of underlying pathology that leads to increased insulin resistance, deterioration of glycemic control, and development of overt type 2 diabetes with dietary intakes of hydrogen peroxide as low as 500 mM. L. L. Hansen et al., Insulin Signaling Is Inhibited by Micromolar Concentrations of H2O2. Evidence for a Role of H2O2 in Tumor Necrosis Factor Alpha-Mediated Insulin Resistance, 274 J. Biol. Chem. 25078-25084 (1999); D. W. Laight et al., Pro-oxidant Challenges In Vivo Provokes the Onset of NIDDM in the Insulin Resistant Obese Zucker Rat, 128 Br. J. Pharmacol. 269-271 (1999).
The impact of oxidative stress mechanism in the pathogenesis of diabetes has been thus far unrecognized and may be so important that development of polyunsaturated fatty acid products like CLA for diabetes prevention and management without taking lipid stability into consideration may reduce the effectiveness of the product or even promote acceleration of underlying pathology.
It is therefore crucial that technology be defined and commercialized for CLA products that will produce greater CLA stability and inhibit the formation of lipid peroxides for extended periods of time in various forms of dietary supplements, foods, and drug compositions and thus improve the bioavailability of the bioactive polyunsaturated lipid isomers in CLA-containing formulas.
In view of the foregoing, it will be appreciated that providing compositions and methods for stabilizing CLA in dietary supplements, foods, and drugs would be a significant advancement in the art.
It is an object of the present invention to provide compositions and methods for stabilizing CLA in dietary supplements, foods, and drugs.
It is also an object of the invention to provide a method for inhibiting or preventing oxidation of CLA for use in dietary supplements, foods, and drugs.
It is another object of the invention to provide a dietary supplement containing CLA formulated such that oxidation of the CLA is inhibited or prevented.
These and other objects can be addressed by providing a dietary supplement comprising a mixture of a glycerol ester of conjugated linoleic acid and an antioxidant ingredient. This ester can be a monoglyceride, diglyceride, triglyceride, or mixtures thereof. The antioxidant ingredient is preferably a member selected from the group consisting of rosemary (Rosmarinus officinalis) leaf extract, tocopherols, ascorbic acid, chelating agents, alpha lipoic acid, BHA, BHT, TBHQ, ascorbyl palmitate, ascorbyl-6-gammalinolenic acid, ascorbyl-6-conjugated linoleic acid, ascorbyl-6-dihomogammalinolenic acid, and mixtures thereof. Such chelating agents can include EDTA, citric acid, and mixtures thereof. In another preferred embodiment of the invention the dietary supplement further comprises a fatty acid, preferably a 10-22 carbon fatty acid or mixture thereof, and most preferably a member of the group consisting of stearic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid, lauric acid, and mixtures thereof.
Another preferred embodiment of the invention comprises a method for supplementing an individual""s diet comprising administering an effective amount of a dietary supplement comprising mixture of a glycerol ester of conjugated linoleic acid and an antioxidant ingredient. In a preferred embodiment of the invention such effective amount comprises about 1-100 mg of conjugated linoleic acid per kg of body weight.